I am working on a project using ATMEGA644 DIP. In this I have written a program for LCD interface which is working fine in Proteus simulation, but on the hardware it is not giving me any response on LCD. As I observed may be my micro controller is not set on the external clock or it can be any other issue also, same program is working fine with ATMEGA32 with 16 Mhz external oscillator. Please help me out. Thanks in advance.

Happy 75th anniversary to one of the best movies ever made! Rick Blane [Bogart]: "Of all the gin joints, in all the towns, in all the world, she walks into mine."

"Some questions have no answers."[C Baird] "There comes a point where the spoon-feeding has to stop and the independent thinking has to start." [C Lawson] "There are always ways to disagree, without being disagreeable."[E Weddington] "Words represent concepts. Use the wrong words, communicate the wrong concept." [J Morin] "Persistence only goes so far if you set yourself up for failure." [Kartman]

On the contrary - I applaud Proteus for getting the simulation right - it spotted that JTAGEN was enabled so prevented C4..7 being using as normal IO. (just like would have happened in the real silicon).

I have tried after making CKSEL3..0 pins disable but still micro controller is not using external crystal.

How are you determining that it is not using the external crystal?

Tell us the precise fuse values (preferably as read out in hexadecimal).

Happy 75th anniversary to one of the best movies ever made! Rick Blane [Bogart]: "Of all the gin joints, in all the towns, in all the world, she walks into mine."

"Some questions have no answers."[C Baird] "There comes a point where the spoon-feeding has to stop and the independent thinking has to start." [C Lawson] "There are always ways to disagree, without being disagreeable."[E Weddington] "Words represent concepts. Use the wrong words, communicate the wrong concept." [J Morin] "Persistence only goes so far if you set yourself up for failure." [Kartman]

Happy 75th anniversary to one of the best movies ever made! Rick Blane [Bogart]: "Of all the gin joints, in all the towns, in all the world, she walks into mine."

"Some questions have no answers."[C Baird] "There comes a point where the spoon-feeding has to stop and the independent thinking has to start." [C Lawson] "There are always ways to disagree, without being disagreeable."[E Weddington] "Words represent concepts. Use the wrong words, communicate the wrong concept." [J Morin] "Persistence only goes so far if you set yourself up for failure." [Kartman]

That could be bad or really bad. Locate the tutorial "Resurrecting a bricked AVR" (or a title similar to that) in the Tutorials forum here at AVRfreaks and read.

Unless you've messed with the SPIEN fuse there are relatively simple ways to fix it.

Lesson to be learned: Do not fiddle with fuses unless you are absolutely sure of what you are doing. (If you need to ask yourself "How do I know if I'm sure?", then you're not.)

Happy 75th anniversary to one of the best movies ever made! Rick Blane [Bogart]: "Of all the gin joints, in all the towns, in all the world, she walks into mine."

"Some questions have no answers."[C Baird] "There comes a point where the spoon-feeding has to stop and the independent thinking has to start." [C Lawson] "There are always ways to disagree, without being disagreeable."[E Weddington] "Words represent concepts. Use the wrong words, communicate the wrong concept." [J Morin] "Persistence only goes so far if you set yourself up for failure." [Kartman]

Now I am getting this error. Is there any solution available for this issue??

Three posts up I told you to go locate a tutorial here on AVRfreaks and read it. With 99% certainty it applies to your problem. In fact, the situation you're in is so common someone decided to instead of answering every time the question was asked, to write a tutorial covering it. Depending on things unknown to both us and you ATM, there is no one distinct solution to your problem. It will be a matter of trial and error. Read the tutorial for the details.

No, no-one will re-type the test of that tutorial just so that you will not need to locate and read it in it's current place.

Happy 75th anniversary to one of the best movies ever made! Rick Blane [Bogart]: "Of all the gin joints, in all the towns, in all the world, she walks into mine."

"Some questions have no answers."[C Baird] "There comes a point where the spoon-feeding has to stop and the independent thinking has to start." [C Lawson] "There are always ways to disagree, without being disagreeable."[E Weddington] "Words represent concepts. Use the wrong words, communicate the wrong concept." [J Morin] "Persistence only goes so far if you set yourself up for failure." [Kartman]

Happy 75th anniversary to one of the best movies ever made! Rick Blane [Bogart]: "Of all the gin joints, in all the towns, in all the world, she walks into mine."

"Some questions have no answers."[C Baird] "There comes a point where the spoon-feeding has to stop and the independent thinking has to start." [C Lawson] "There are always ways to disagree, without being disagreeable."[E Weddington] "Words represent concepts. Use the wrong words, communicate the wrong concept." [J Morin] "Persistence only goes so far if you set yourself up for failure." [Kartman]

But this leaves your CLKDIV8 switch still programmed, so the ATmega644 will run 8 times slower than the crystal. clearing the CLKDIV8 engbedded.com computes

Low: 0xEF

High: 0x99

Extendec: 0xFF

But, since you likely have "bricked" your AVR (by programming some unknown but really bad fuse values) you first need to try to fix that, as described in the thread i linked to above.

Happy 75th anniversary to one of the best movies ever made! Rick Blane [Bogart]: "Of all the gin joints, in all the towns, in all the world, she walks into mine."

"Some questions have no answers."[C Baird] "There comes a point where the spoon-feeding has to stop and the independent thinking has to start." [C Lawson] "There are always ways to disagree, without being disagreeable."[E Weddington] "Words represent concepts. Use the wrong words, communicate the wrong concept." [J Morin] "Persistence only goes so far if you set yourself up for failure." [Kartman]